1. Field of the Invention
The present invention relates to a modular battery. More particularly, the present invention relates to a high power and large capacity battery module having an improved connection member between unit cells.
2. Description of the Related Art
A rechargeable or secondary battery is generally distinguished from a primary battery in that it can be repeatedly charged when discharged. A rechargeable battery with low capacity is used for small portable electronic devices such as mobile phones, laptop computers, and camcorders. On the other hand, a rechargeable battery with high capacity can be used as a power source for driving a motor of a hybrid electric automobile and the like. A plurality of low capacity rechargeable batteries may be connected in series to form a battery module with high capacity so that it may be used for driving a motor of an electric vehicle requiring a large amount of electric power.
The battery module or modular battery generally includes a plurality of rechargeable batteries, which are often referred to as unit cells (hereinafter “unit cells” for convenience). The unit cells respectively include an electrode assembly, which is composed of positive and negative electrodes and a separator interposed therebetween, a case having a space for housing the electrode assembly, a cap assembly combined with the case and sealing it, and positive and negative terminals that are electrically coupled to respective positive and negative electrodes.
The rechargeable batteries or unit cells are mainly formed in a cylindrical or prismatic shape. In the prismatic configurations, the positive and negative terminals typically externally protrude out of the cap assembly, so that it can be exposed to outside the unit cell.
When the unit cells forms a battery module, they are arranged such that the positive terminal of one unit cell is close to the negative terminal of a neighboring unit cell. Then, the positive and negative terminals are connected each other through a connection member (conductor). The connection member may be fastened to positive and negative terminals by nuts or other mechanisms. The positive and negative terminals may have threads like a bolt so as to be coupled with nuts.
Typically, the connection member is formed in a single piece with two engagement portions or means apart from each other at a distance. One engagement portion or means is to be engaged with the positive terminal of one unit cell, and the other is to be engaged with the negative terminal of an immediately neighboring unit cell. The engagement portions or means may be a hole through which an externally protruding terminal can be inserted. When the terminals are threaded, nuts may be used to secure the connection member to the terminals.
When the distance between two neighboring unit cells is not exact and therefore the distance between the two terminals to be connected with a connection member, connecting the connection members with terminals of unit cells may become difficult. Given the configuration of the connection members, the distance between two neighboring unit cells should be precisely controlled. When the design of the parts of the unit cells is changed and the distance changes, the difficulty can realize. Thus, there is a need to improve the design of the connection member that can accommodate the changes in the distance.
The above information in this background section is only for the understanding of the background of the invention, and no statement in this section constitutes an admission of prior art.